You have a solution of unknown concentration. You place this solution in your spectrometer and measure that it has an absorbance of 0.4 at 450 nm. The molar absorptivity of your product is 1500 L/moles·cm. Assuming that you are measuring the sample in a 1 cm path length cell what is the concentration of product in your solution? Report your answer in mM units.

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anfabba15 anfabba15 · Answer 1 · 2020-03-07T14:35:05+01:00

Answer:

Concentration of solution is 0.27 mM

Explanation:

We apply Lambert-Beer law to solve this problem of spectrometry:

Abs = a . L . C

where a is absorptivity, L is the length of the cuvette and C, concentration (M).

Abs is the absorbance of the solution which is readed by the spectrometer

0.4 = 1500 L/mol.cm . 1cm . C

0.4 / 1500 mol/L = C

2.67×10⁻⁴ mol/L = C

To convert the units to mM, we need to make this conversion

2.67×10⁻⁴ mol . 1000 mmoles/ 1 mol = 0.27 mM

throwdolbeau throwdolbeau · Answer 2 · 2022-03-08T12:53:51+01:00

Concentration of solution is 0.27 mM.

There is a linear relationship between the concentration and the absorbance of the solution

A =E* l * c

where,

E is molar absorptivity,

l is the path length of the cuvette,

A is the absorbance

c is the concentration (M)

On substituting the values:

0.4 = 1500 L/mol.cm . 1cm . c

0.4 / 1500 mol/L = c

2.67×10⁻⁴ mol/L = c

Unit conversion:

2.67×10⁻⁴ mol . 1000 mmoles/ 1 mol = 0.27 mM

Thus, the concentration of solution is 0.27 mM.

Find more information about Lambert-Beer's law here:

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